1948. The shadow of war still lingers over Britain and Beattie Cavendish, former Secret Operations Executive agent, refuses to settle into civilian life. When offered an undercover role at the newly formed GCHQ, the nerve centre of Britain's intelligence network, she doesn't hesitate. Her first mission is to infiltrate the powerful Bowen family and find out what she can about politician Ralph Bowen who is suspected of being a communist sympathiser.

Her mission takes a deadly turn when the Bowen's housekeeper, Sofia, has her throat cut. As the investigation spirals, Beattie teams up with war-weary detective Patrick Corrigan to expose a dangerous web of spies and secrets all leading back to The White Pearl Club, a Soho establishment that caters to gentlemen with dangerous appetites.

As powerful forces attempt to bury the truth, Beattie must survive a ruthless game of deception and the dark underbelly of 1940s Soho at the dawn of the Cold War.